Dampener for lithographic printing



June 23, 1959 N. L. ROWE ET AL 2,891,470

DAMPENER FOR LITHOGRAPHIC PRINTING Filed Oct. 25, 1956 June 23, 1959 N. L. RQWE ETAL 2,891,470

DAMPENER FOR LITHOGRAPHIC PRINTING Filed Ocfi. 23, 1956 I 2 Sheets-Sheet 2 zz mow-mam L Q uae.

Trams 2,891,470 FOR LlTI-IOGRAPHIC PRINTING Norman L. Rowe and Gustave Reischl, Long City, N.Y., assignors' to Ideal Roller and Manufacturing Company, Chicago, a corporation of Illinois Application Qctober 23, 1956, Serial No. 617,791 fsclsnms. c1. 101-1148 This invention relates to a rotary dampener for use in lithographic printing comprising a base roll of resiliently yieldable material having a surface covering composed of a sheet of vegetable parchment paper to provide water receptive properties superior to the knitted molleton commonly used.

One object is to attach the parchment sheet to the base roll in a novel manner which facilitates use of the dampener in a lithographic printing press and which permits removal and replacement of the parchment covering without the necessity of resetting the dampener in the press.

Another object is to correlate the construction of the base roller with the parchment wrapping so as to provide extremely uniform contact pressure between the dampener and the plate cylinder.

The invention also resides in the novel manner of attaching the parchment covering to the ends of the base roll.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a schematic view of the elements of a lithographic printing press for utilizing the improved dampener.

Figs. 2 and 3 are plan and cross-sectional views of the improved dampener.

Figs. 4 and 5 are fragmentary enlarged views of the roller end illustrating alternative forms of fastenings for the parchment covering.

Fig. 6 is a perspective view illustrating the manner of forming the parchment covering.

Fig. 7 is an enlarged fragmentary section of the starting end of the roller shown in Fig. 6.

In the operation of a lithographic printing press, the improved dampener indicated at 10 receives water from a contacting rigid intermediate roll 11 and runs in contact with the plate 12 on a cylinder 13. As a result, the nonprinting areas 14 of the plate are wetted and thus adapted to prevent the transfer of ink from the inking roll 15 except on the sensitized areas 16.

The improved dampener comprises generally a shaft 17 supported from its projecting ends 18 and covered with a tubular base 19 composed of resiliently yieldable material such as rubber which is made considerably softer than the base rolls heretofore used with ordinary knitted molleton coverings. The hardness of the base surface is within a range of 5 to 15 as determined by a Shore A durometer, the preferred softness being about 10.

For a purpose to appear later, the working cylindrical surface of the base roll terminates at ends or shoulders 20 leaving end portions 21 of reduced diameter and of cylindrical contour in this instance. Usually these end portions are about a half inch wide and of a diameter about of an inch less than the working surface.

The water receptive covering indicated at 22 comprises a tube tightly adhering to the rubber surface and comice I t posed of vegetable parchment paper which has been found to possess unusual water receptive and distributing properties contributing to an improved quality of the printing as compared to the molleton type of dampener. The parchment paper is of standard composition and about .003 of an inch thick.

In accordance with the present invention, the paper. is applied to the base roll in the form of-an elongated strip 23 having a width only a small fraction of the length of the base working surface, the strip being wrapped helically around the base surface through a plurality of revolutions with the adjacent convolutions overlapping each other to form double thickness bands 24 alternatingv along the length of the finished roller with intervening single layer bands 25. The strip 23 is preferably about 3 inches wide and is formed by cutting a standard sheet of vegetable parchment paper to the desired width in a continuous slitting operation so as to avoid any possibility of leaving roughened edges with projections which are free to flex after attachment of the strip to the base roll. This overlap is preferably about 4 inch.

The helical wrapping is in the direction of rotation of the roll during its operation in a printing press and extends beyond the ends 20 of the working surface so that the tube formed by the helical wrapping extends well beyond these ends and encircles the reduced end portions 21 as shown in Fig. 7. The helix angle of the wrap depends on the diameter of the base roll and is such as to always provide the overlap above referred to.

While the wrapping may be effected while the strip 23 is dry, it is ordinarily easier to avoid wrinkles by wetting the strip thoroughly before it is appiled to the base roll. To this end, a length of the parchment strip sufficient to cover the full length of the working surface of the base roll is measured off and thoroughly wetted by soaking in water. One end of the wetted strip is laid against the base roll surface at the proper helix angle and overlapping the reduced portion 21 at one end of the base roll. By turning the roll slowly while maintaining the unwrapped portion of the strip taut, the entire length may be wound at the proper helix angle around the base roll and caused to hug the latter tightly without wrinkling and with the adjacent convolutions overlapping each other to form the bands 24. The circumeferentially continuous tubular covering thus formed is not only contracted tightly around the base roll but extends beyond the shoulders 20 as indicated at 26. After squaring off these projecting ends, while the latter are still wet, they may be bent inwardly around the shoulders and thus contracted against the surface of the end portions 21 without danger of folding or wrinkling at any point which is to contact the printing plate in service operation. The overlapping ends 26 thus contracted may be secured to the base roll in various ways, one being by a rubber band 27 encircling the wet and contracted portion of the tube as shown in Fig. 4. Or, a band 28 of adhesive tape may be wrapped around the contracted tube as shown in Fig. 5.

With the parchment paper covering thus formed and attached to the yieldable surface of a base roll of the preferred softness, the differences in the thicknesses of the alternating areas 24 and 25 does not affect the uniformity of the pressure of contact between the dampener roll and the printing plate in service operation. As a result, the desired uniformity in contact pressure all along the length of the dampener is achieved thus making it possible to remove and replace the parchment covering without the necessity of readjusting the position of the dampener in the printing press.

We claim as our invention:

1. In a lithographic printing press having a plate cylinder and a dampener urged against said cylinder under a predetermined pressure to distribute water to the plate,

Patented June 23, 1959.

3 s'aiddampener comprising abase roll having a cylindrical surfaceofresilient material yieldable under pressure, and a strip of vegetable parchment paper substantially narrower than the length of said cylindrical surface Wrapped closely aroundsaid surface through a plurality of revolutions toform a tube longer than said surface and closely fitting but detached from the latter at all points, the adjacent convolutions of said tube overlapping each other along the said surface to form areas of single and double thickness alternating with each other along the full length of said surface, and the ends of said tube beyond said surface being contracted to a diameter smaller than that of said surface, said resilient surface being of a hardness within the range of about 5 to about 15- as determined by a Shore A Durometer, whereby the yieldability of said surface is suflicient to permit depression of said double thickness areas under said v 4 7 pressure and the consequent reshaping of said tube to a uniform diameter over'its' entire outer cylindrical "surface:

2. A lithographic printing press as defined in claim 1, wherein the said resilient surface is of a hardness of about 10 as determined by a Shore A Durometer.

3. A lithographic printing press as defined in claim 1, including means encircling. the ends of said tube and holding said ends contracted to a-diarneter smaller than that of'said cylindrical surface.

References Cited in the'file of this patent UNITED STATES PATENTS 1,789,244 McCollurn Jan. 13,- 1931 2,429,670 Crews Oct. 28, 1947 2,775,195 Martin Dec. 25, 1956 2,787,213 Hubbard Apr. 2, 1957 

